Originally Posted by Interstella5555
It will never cease to amaze me that people thing something is wrong with their computer when the fans turn on....
If you're a (former) PC guy/gal then the Mac is a lot different than what you're used to. Especially with the fans/heat situation of a rMBP (not sure about the cMBP as I don't own it). The fans are a lot more active in a rMBP due to the aluminum casing and the tight tolerances within it. It took me 2 weeks of monitoring the temps and fans under load (using the log in the Temperature Gauge app), and downloading and monitoring iStat Menus and smcFanControl to feel comfortable enough to accept the heat the rMBP generates as normal. Load temps of 60, 70 or even 80-85 degrees Celsius playing D3, or watching a 4K vid in YouTube, or 1080p streaming on Twitch.tv is normal in this machine (unless you repaste). As such the fans will be much more active.
If you're used to the plastic casing of most PC notebooks then the heat/fans running for these tasks won't seem normal. That said I completely sympathize with these posts.